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Ive been reading bits and pieces over the last weeks about bending moments of the metatarsals.

Over this time Ive come to think abouit Wolfs law. . Nice and simple increase load > bone growth. The more the load the thicker the bone.

But since reading these 3 articles Ive come to the point that we maybe able to use wolf´s law a guide the level and direction of Bending moments over many years. This may make our orthotic prescription better customised. Of course it may only be theorical and have no bearing in the real world.

Article 1 suggested read by Kevin about bending moments in the metatarsals

Articel 2 Bending moments in the 2 met and then effect of heel lift and muscle balnce on these moments

Article 3 Bending moments in long bone ( this is research in sheep and primates) but the maths show that bending moments are not linear.

From these calculations we maybe able to work backwards and work out where the casue of the bending moment is comming from and design more specific custom orthotic or treatment plan in the case of muscle fatigue.

Ive been reading bits and pieces over the last weeks about bending moments of the metatarsals.

Over this time Ive come to think abouit Wolfs law. . Nice and simple increase load > bone growth. The more the load the thicker the bone.

But since reading these 3 articles Ive come to the point that we maybe able to use wolf´s law a guide the level and direction of Bending moments over many years. This may make our orthotic prescription better customised. Of course it may only be theorical and have no bearing in the real world.

Article 1 suggested read by Kevin about bending moments in the metatarsals

Articel 2 Bending moments in the 2 met and then effect of heel lift and muscle balnce on these moments

Article 3 Bending moments in long bone ( this is research in sheep and primates) but the maths show that bending moments are not linear.

From these calculations we maybe able to work backwards and work out where the casue of the bending moment is comming from and design more specific custom orthotic or treatment plan in the case of muscle fatigue.

thinking too much or something to consider ?

Click to expand...

Michael:

You should also read this recent research article by Erin Ward, DPM, and coworkers where 2nd metatarsal strain was significantly more affected by custom orthoses than semi-custom orthoses during "walking" of cadaver feet in a dynamic gait replicator.

What do you and or others think of the idea of using bone measurments to show what
10 000´s of foot strikes have had on the foot to work out where the force has come from and using that as 1 of the guides to presription writing?

What do you and or others think of the idea of using bone measurments to show what
10 000´s of foot strikes have had on the foot to work out where the force has come from and using that as 1 of the guides to presription writing?

Click to expand...

Michael:

Bone strain can be modeled using finite element analysis and can be estimated also using such techniques as free body diagrams.

First, it is a given that all bones undergo deformation (i.e. strain) during weightbearing activities. The longer bones that are more narrow will bend more for a given load than will other bones. Engineering principles tells us that the first metatarsal will bend less with a given plantar metatarsal head load than the second metatarsal would bend with an equivalent plantar load added to the second metatarsal head. This is due to the greater cross-sectional area, or area moment of inertia, of the first metatarsal compared to the second metatarsal.

Secondly, patients will complain of bone pain or bones will become tender some time before bone fracture occurs in repetitive microtrauma injuries. Cases of repetetive excessive bone strain such as metatarsal stress reactions or medial tibial stress syndrome will cause the bone to become painful or tender to palpation well before a fracture occurs. So, the intelligent clinician, when detecting tenderness along the long bones of the foot and lower extremity, will already know that excessive bone bending may be the cause of this long bone pain.

One test that I have used over the last decade is that I will commonly palpate deeply on the dorsal aspects of the metatarsal necks in my patients that complain of diffuse forefoot pain to find which metatarsal shaft is most tender. The most tender one is likely the one that will show a stress reaction on the MRI, without needing to spend $1,000 or more on the MRI to start diagnosing and treating the injury, a "pre-stress fracture of the metatarsal".

When I treat patients, I use my understanding of mechanical modelling techniques for the foot and lower extremity to allow me to be a better clinician so that, if I see pain in a certain location, I can more effectively determine the most likely mechanical cause of the pain. This is the basis of using tissue stress theory to more effectively treat patients with mechanically-related pathologies of the foot and lower extremity.

Abstract
The law of bone remodeling, commonly referred to as Wolff's Law, asserts that the internal trabecular bone adapts to external loadings, reorienting with the principal stress trajectories to maximize mechanical efficiency creating a naturally optimum structure. The goal of the current study was to utilize an advanced structural optimization algorithm, called design space optimization (DSO), to perform a micro-level three-dimensional finite element bone remodeling simulation on the human proximal femur and analyse the results to determine the validity of Wolff's hypothesis. DSO optimizes the layout of material by iteratively distributing it into the areas of highest loading, while simultaneously changing the design domain to increase computational efficiency. The result is a “fully stressed” structure with minimized compliance and increased stiffness. The large-scale computational simulation utilized a 175μm mesh resolution and the routine daily loading activities of walking and stair climbing. The resulting anisotropic trabecular architecture was compared to both Wolff's trajectory hypothesis and natural femur samples from literature using a variety of visualization techniques, including radiography and computed tomography (CT). The results qualitatively revealed several anisotropic trabecular regions, that were comparable to the natural human femurs. Quantitatively, the various regional bone volume fractions from the computational results were consistent with quantitative CT analyses. The global strain energy proceeded to become more uniform during optimization; implying increased mechanical efficiency was achieved. The realistic simulated trabecular geometry suggests that the DSO method can accurately predict bone adaptation due to mechanical loading and that the proximal femur is an optimum structure as the Wolff hypothesized.

What do you and or others think of the idea of using bone measurments to show what
10 000´s of foot strikes have had on the foot to work out where the force has come from and using that as 1 of the guides to presription writing?

Click to expand...

So, if you wanted to show, using bone measurements, where the areas of high stress was, I think it could work. You might have to make some assumptions about the starting thickness of the bone to compare with the thickness you see at the time of measurement. However, bone measurements may not be the most simple test. I used to joke that the force plate was $10,000 machine that would tell us where the calluses are. Another favorite place of mine to look is the sock liner of the shoe. If they have been using it regularly for about a month you can get some pretty good information for writing your prescription.

So, if you wanted to show, using bone measurements, where the areas of high stress was, I think it could work. You might have to make some assumptions about the starting thickness of the bone to compare with the thickness you see at the time of measurement. However, bone measurements may not be the most simple test. I used to joke that the force plate was $10,000 machine that would tell us where the calluses are. Another favorite place of mine to look is the sock liner of the shoe. If they have been using it regularly for about a month you can get some pretty good information for writing your prescription.

Eric

Click to expand...

Eric I guess it´s just one of the pie in the sky random ideas you get (I do anyway), the maths looks very complicated to me and as you say a sock liner probably give you similar information .